Relatives of murdered pensioner Roseann Mallon have rejected claims that spying equipment trained on their property was incapable of filming at night.

The Army had been running a secret surveillance operation monitoring the movements of her two nephews but an inquest looking into the 1994 shooting has repeatedly heard how the camera was not fitted with infra-red night vision.

"It is inconceivable that the surveillance equipment did not have the capacity to observe at night time," a Mallon family statement said today after it was disclosed that a coroner's court hearing will have to be delayed.

Ms Mallon, 76, was gunned down at her sister-in-law's home on Cullenrammer Road, Dungannon shortly before midnight on May 8, 1994.

The Ulster Volunteer Force said its mid-Ulster unit had been targeting her relatives who were involved in the republican movement.

Notorious loyalist killer Billy Wright was among those arrested and questioned about the attack but no one was ever convicted.

Claims of security force collusion emerged after a camera and transmitter were found in a field overlooking the Mallon house and adjacent engineering works frequented by the spinster's nephews, Martin and Christopher Mallon.

Three separate Army regiments were involved in the covert surveillance operation.

But the Mallon family said they believed other units were also operating in the area at that time.

In a statement issued through the victims' campaign group Relatives for Justice they said: "At the time Roseann was killed there was a sophisticated and highly resourced covert operation outside the house. This operation involved three known separate regiments of the British army, and additional unspecified regiments. It was sanctioned at the highest levels. We found one camera, we know that there were more."

Earlier, Norman Newell, a senior forensic scientist who examined the camera equipment found buried in the ground concealed with bird's nest materials, told the court it did not have a night sight.

Mr Newell also carried out tests which showed how the footage was affected by diminishing levels of light.

He said: "I was able to confirm that below 72 lux (dusk) the camera image was so bad that it was really unwatchable. It would have been worse with the bird's nest concealer.

"So my findings confirmed what I had read in the MoD document."

The non-jury inquest, which is in its second week, is one of 29 controversial Troubles-related legacy cases and has been awaiting a full hearing for almost two decades.

It is being heard by High Court Judge Mr Justice Weir and was scheduled to conclude next week.

Sean Doran, barrister for the Coroner's Service, said proceedings were facing further delay because forensic analysis of the murder weapon had not been complete.

The Historical Enquiries Team, a specialist police unit set up to investigate cold case killings, has ordered an examination of the automatic rifle used b ut a report on the findings has not been submitted to the inquest because the scientist involved is engaged with a criminal trial.

Ordering that the report be made available by November 22, Judge Weir said: "If I find out that the report is half a page I will be very displeased that we have all had to wait two weeks for it.

"The idea that a forensic scientist would spend the next fortnight standing about outside the door of some courtroom is very difficult to swallow."

Last week the inquest heard how the high velocity weapon was part of a consignment brought into Northern Ireland in 1987 and was the weapon of choice for loyalist paramilitaries.

It was found hidden under a piece of corrugated tin in a field close to the scene almost a week after the killing.

Dennis Rooney, barrister for the police and military, said he was reliably informed the forensic report would be ready by November 22.